/*
 * Copyright (c) 2014-2017, ARM Limited and Contributors. All rights reserved.
 *
 * SPDX-License-Identifier: BSD-3-Clause
 */

#include <assert.h>
#include <debug.h>
#include <io_driver.h>
#include <io_storage.h>
#include <string.h>
#include <utils.h>

/* As we need to be able to keep state for seek, only one file can be open
 * at a time. Make this a structure and point to the entity->info. When we
 * can malloc memory we can change this to support more open files.
 */
typedef struct {
    /* Use the 'in_use' flag as any value for base and file_pos could be
     * valid.
     */
    int        in_use;
    uintptr_t    base;
    size_t        file_pos;
    size_t        size;
} file_state_t;

static file_state_t current_file = {0};

/* Identify the device type as memmap */
io_type_t device_type_memmap(void)
{
    return IO_TYPE_MEMMAP;
}

/* Memmap device functions */
static int memmap_dev_open(const uintptr_t dev_spec, io_dev_info_t **dev_info);
static int memmap_block_open(io_dev_info_t *dev_info, const uintptr_t spec,
                 io_entity_t *entity);
static int memmap_block_seek(io_entity_t *entity, int mode,
                 ssize_t offset);
static int memmap_block_len(io_entity_t *entity, size_t *length);
static int memmap_block_read(io_entity_t *entity, uintptr_t buffer,
                 size_t length, size_t *length_read);
static int memmap_block_write(io_entity_t *entity, const uintptr_t buffer,
                  size_t length, size_t *length_written);
static int memmap_block_close(io_entity_t *entity);
static int memmap_dev_close(io_dev_info_t *dev_info);


static const io_dev_connector_t memmap_dev_connector = {
    .dev_open = memmap_dev_open
};


static const io_dev_funcs_t memmap_dev_funcs = {
    .type = device_type_memmap,
    .open = memmap_block_open,
    .seek = memmap_block_seek,
    .size = memmap_block_len,
    .read = memmap_block_read,
    .write = memmap_block_write,
    .close = memmap_block_close,
    .dev_init = NULL,
    .dev_close = memmap_dev_close,
};


/* No state associated with this device so structure can be const */
static const io_dev_info_t memmap_dev_info = {
    .funcs = &memmap_dev_funcs,
    .info = (uintptr_t)NULL
};


/* Open a connection to the memmap device */
static int memmap_dev_open(const uintptr_t dev_spec __unused,
               io_dev_info_t **dev_info)
{
    assert(dev_info != NULL);
    *dev_info = (io_dev_info_t *)&memmap_dev_info; /* cast away const */

    return 0;
}



/* Close a connection to the memmap device */
static int memmap_dev_close(io_dev_info_t *dev_info)
{
    /* NOP */
    /* TODO: Consider tracking open files and cleaning them up here */
    return 0;
}


/* Open a file on the memmap device */
static int memmap_block_open(io_dev_info_t *dev_info, const uintptr_t spec,
                 io_entity_t *entity)
{
    int result = -ENOMEM;
    const io_block_spec_t *block_spec = (io_block_spec_t *)spec;

    /* Since we need to track open state for seek() we only allow one open
     * spec at a time. When we have dynamic memory we can malloc and set
     * entity->info.
     */
    if (current_file.in_use == 0) {
        assert(block_spec != NULL);
        assert(entity != NULL);

        current_file.in_use = 1;
        current_file.base = block_spec->offset;
        /* File cursor offset for seek and incremental reads etc. */
        current_file.file_pos = 0;
        current_file.size = block_spec->length;
        entity->info = (uintptr_t)&current_file;
        result = 0;
    } else {
        WARN("A Memmap device is already active. Close first.\n");
    }

    return result;
}


/* Seek to a particular file offset on the memmap device */
static int memmap_block_seek(io_entity_t *entity, int mode, ssize_t offset)
{
    int result = -ENOENT;
    file_state_t *fp;

    /* We only support IO_SEEK_SET for the moment. */
    if (mode == IO_SEEK_SET) {
        assert(entity != NULL);

        fp = (file_state_t *) entity->info;

        /* Assert that new file position is valid */
        assert((offset >= 0) && (offset < fp->size));

        /* Reset file position */
        fp->file_pos = offset;
        result = 0;
    }

    return result;
}


/* Return the size of a file on the memmap device */
static int memmap_block_len(io_entity_t *entity, size_t *length)
{
    assert(entity != NULL);
    assert(length != NULL);

    *length = ((file_state_t *)entity->info)->size;

    return 0;
}


/* Read data from a file on the memmap device */
static int memmap_block_read(io_entity_t *entity, uintptr_t buffer,
                 size_t length, size_t *length_read)
{
    file_state_t *fp;
    size_t pos_after;

    assert(entity != NULL);
    assert(buffer != (uintptr_t)NULL);
    assert(length_read != NULL);

    fp = (file_state_t *) entity->info;

    /* Assert that file position is valid for this read operation */
    pos_after = fp->file_pos + length;
    assert((pos_after >= fp->file_pos) && (pos_after <= fp->size));

    memcpy((void *)buffer, (void *)(fp->base + fp->file_pos), length);

    *length_read = length;

    /* Set file position after read */
    fp->file_pos = pos_after;

    return 0;
}


/* Write data to a file on the memmap device */
static int memmap_block_write(io_entity_t *entity, const uintptr_t buffer,
                  size_t length, size_t *length_written)
{
    file_state_t *fp;
    size_t pos_after;

    assert(entity != NULL);
    assert(buffer != (uintptr_t)NULL);
    assert(length_written != NULL);

    fp = (file_state_t *) entity->info;

    /* Assert that file position is valid for this write operation */
    pos_after = fp->file_pos + length;
    assert((pos_after >= fp->file_pos) && (pos_after <= fp->size));

    memcpy((void *)(fp->base + fp->file_pos), (void *)buffer, length);

    *length_written = length;

    /* Set file position after write */
    fp->file_pos = pos_after;

    return 0;
}


/* Close a file on the memmap device */
static int memmap_block_close(io_entity_t *entity)
{
    assert(entity != NULL);

    entity->info = 0;

    /* This would be a mem free() if we had malloc.*/
    zeromem((void *)&current_file, sizeof(current_file));

    return 0;
}


/* Exported functions */

/* Register the memmap driver with the IO abstraction */
int register_io_dev_memmap(const io_dev_connector_t **dev_con)
{
    int result;
    assert(dev_con != NULL);

    result = io_register_device(&memmap_dev_info);
    if (result == 0)
        *dev_con = &memmap_dev_connector;

    return result;
}
